1. Field of the Invention
This invention relates to longwall mining systems and more specifically relates to longwall mining haulage having unique pinion and rack members for use in such systems.
2. Description of the Prior Art
In longwall mining, a cutting machine which is used to extract minerals, such as coal, moves in a direction generally parallel to the mineral face and is provided with one or more rotary cutting drums which serve to engage the face and free the mineral. The mineral which has been freed is delivered to a conveyor positioned generally parallel to the mine face for removal from the mining site. Longwall miners are generally operated in a reversible fashion. After translational movement of the machine during a cutting operation in a first direction the direction of machine travel is reversed and cutting is effected while the machine moves in the opposite direction.
It has been known to employ various means for effecting translational movement of mining machines. One conventional means for effecting such longwall mining machine movement is the use of a chain and sprocket arrangement. See for example, U.S. Pat. Nos. 1,704,667; 3,409,329; 3,418,023; 3,602,549; and 3,753,595. It has also been suggested to employ for longwall machine haulage a sprocket which cooperates with a pocketed guide rod having reciprocating pegs which are adapted to engage the sprocket. See U.S. Pat. No. 3,753,596.
It has also been known to effect haulage of mining machines generally by means of rack and pinion drives. See U.S. Pat. Nos. 563,776; 158,125; and 1,704,667. Rack and pinion drives have also been employed in connection with longwall mining machine haulage. See for example U.S. Pat. No. 3,954,300.
There remains a need for a longwall rack and pinion haulage system which provides more efficient haulage. There is a further need for such system wherein the rack and pinion haulage combination can serve to facilitate delivery of freed mineral from a potentially interfering position within the rack to the desired delivery position on the conveyor.